1. Technical Field
The present invention relates to an optical device unit and a detection apparatus.
2. Related Art
In general, a Raman spectroscopic apparatus includes a detector for obtaining Raman spectra by detecting Raman scattering light depending on a detection target substance. The detection target substance can be specified by performing a spectroscopic analysis using the Raman spectra. However, the signal intensity of the Raman scattering light is typically weak, and its detection sensitivity is low.
JP-T-2008-529006 discloses a handheld Raman blood analyzer to provide surface-enhanced Raman scattering using gold colloid sol-gel/strips and increase the signal intensity of the Raman scattering light.
In addition, a localized plasmon can be generated by irradiating excitation light onto a metal surface. The electric field can be locally enhanced by combining the excitation light and the localized plasmon. It is envisaged that Raman scattering light is enhanced by the enhanced electric field in the surface-enhanced Raman scattering.
Japanese Patent No. 3,482,824 discloses a vertical cavity surface-emitting laser (VCSEL) capable of safely controlling a polarization surface in which excitation light can be provided using the VCSEL.
Optical absorption is generated by localized plasmon resonance when excitation light and localized plasmon are combined. For example, JP-A-2000-356587 discloses a technique of improving sensor sensitivity based on localized surface plasmon resonance using a substrate having a surface where metal micro particles are fixed. JP-A-2007-10648 discloses a localized plasmon resonance sensor having a resonance peak shifted to a long wavelength side and a resonance peak shifted to a short wavelength side. In addition, JP-A-2009-250951 discloses an electric field enhancement device including a micro resonator having a plurality of resonance areas in order to make it possible to resonate for a plurality of wavelengths.
A Raman spectroscopic apparatus typically includes an optical device having an electrical conductor such as a metal nano-structure where a detection target substance can be adsorbed. Raman scattering light caused by an enhanced electric field can be detected by guiding the target substance into the enhanced electric field near the optical device. Depending on the type of target substance, or the type of an optical device, signal intensity of the Raman scattering light may not be stable.